The invention relates to waterbed mattress construction and more particularly to the design of baffles used to dampen wave action in waterbeds.
One of the problems encountered in conventional waterbed design is the presence of wave motion within the waterbed mattress. A conventional waterbed comprises a water retaining bladder supported along its sides by a wooden frame. Where there is no provision for damping of wave motion within the mattress, movement of the person on the water-retaining bladder will generate waves within the bladder which reflect off the sides of the frame causing standing waves within the bladder at a resonant frequency depending on the volume of the bladder. This wave action is disturbing to the individual sleeping on the mattress.
Consequently, various means for damping the wave action have been attempted. For example, support frames having inclined side walls have been designed to reduce wave reflection, and fibrous materials have been introduced into the water to dampen wave motion. Various baffle constructions in the interior of the waterbed bladder have also been provided. Fogel Canadian Patent no. 1,100,238 provides elongated sheet baffles which are welded to the bottom inner surface of the bladder and are provided with flotation rods along the top edge of the baffle to extend it vertically in the interior of the bladder. Carson U.S. Pat. No. 3,736,604 discloses internal sheet baffles which are welded to the upper inner surface of the bladder and are weighted to hang downwardly. Labianco U.S. Pat. No. 3,840,921 discloses internal sheet baffles which are welded to the inner surface of the bladder along both top and bottom edges. None of these designs have been completely successful in damping wave action.
Another attempted solution to the damping of wave motion has been the provision of damping chambers in the interior of the bladder. Such a construction is shown in Carpenter U.S. Pat. No. 4,325,152. The damping chambers in this design are hollow right circular cylinders having flexible walls which are provided with a number of openings which allow the flow of water into and out of the interior of the chambers. The openings are symmetrically arranged circular holes with two sets of four holes being vertically spaced, the holes in each group of four being disposed at about 90 degrees from the horizontally adjacent hole. The holes comprise about 25 to 35 percent of the surface area of the cylinder. The lower end of the cylindrical chamber is fixed to the lower inner surface of the bladder, and the top end floats freely due to the provision of a disk of buoyant material held adjacent the upper inner surface of the cylinder. In this way the chambers extend vertically in the interior of the bladder to dampen wave action, and when the upper surface of the mattress is displaced downwardly, the interior surface of the bladder deforms the chamber and causes water to be expelled in different directions from the openings in the chamber, further impeding wave action.
A problem with such baffle structures which are welded to the waterbed mattress is that considerable stresses are placed on the joints and eventually either the baffle will break away from the bladder, thus reducing the wave damping function, or a leak will be created in the bladder itself. The firmer such mattresses are made (the greater the restriction on water flow out of the cylindrical chambers) the greater the stresses on the joints.
Phillips U.S. Pat. No. 4,475,257 discloses the use of an array of damping baffles or cells, each attached at its upper end to a top panel and each closed at its lower end except for a central aperture. The lower end is spaced above the bottom of the mattress in use. Each cell has its own flotation plate, and the top panel as a whole is free-floating. The top panel is provided with a circular array of holes in the vicinity of each cell which are closed by contact with the flotation plate when the top of the cell is forced downwardly. There is an array of secondary holes around the lower portion of the cell which are open when the cell is extended but close when it is compressed. In this way, apparently, bottoming out of the mattress is reduced while rapid recovery of the cells when pressure is removed is permitted. Smith U.S. Pat. No. 4,663,789 discloses a similar construction in which the lower end of the cells is attached to a free-floating panel while the upper ends are unconnected and provided with flotation panels. Such freefloating systems have not adequately solved the problem of wave action.
Fogel U.S. Pat. No. 4,715,076 discloses a two-part baffle, with inner and outer chambers, to provide wavelessness and firmness, but such baffles are difficult to manufacture.
There is therefore a need for a wave-damping baffle which reduces the problem of stress on the point of attachment of the baffle to the bladder while also preserving a firmness in the mattress.